Graft copolymers of an acrylic acid ester/butadiene copolymer, styrene and acrylonitrile



United States Patent (3 2,994,683 GRAFT COPOLYMERS OF AN ACRYLIC ACIDESTER/BUTADIENE COPOLYMER, STYRENE AND ACRYLONITRILE William C. Calvert,Gary, Ind., assignor to Borg-Warner Corporation, Chicago, 111., acorporation of Illinois No Drawing. Continuation of application Ser. No.691,800, Oct. 2 3, 1957. This application Dec. 39,

1959, Ser. No. 862,794

7 Claims. (Cl. 260-455) This application is a continuation ofapplication Serial No. 691,800, filed October 23, 1957, now abandoned,for Graft Copolymers of an Acrylic Acid Ester/Butadiene Copolymer,Styrene and Acrylonitrile.

The present invention relates to graft copolymers of an acrylic acidester/butadiene copolymer, styrene and acrylonitrile. As used in thisspecification, and as defined in the Report on Nomenclature of theInternational Union of Pure and Applied Chemistry, Journal of HighPolymer Science, volume 8, page 260, the term graft copolymer designatesa high polymer, the molecules of which consist of two or more polymerparts of different compositions, chemically united together. A graftcopolymer may be produced, for example, by polymerization of a givenkind of monomer with subsequent polymerization of another kind ofmonomer onto the product of the first polymerization. Most conveniently,graft copolymerization reactions are conducted by the emulsionpolymerization technique although it is possible, but generally muchless convenient, to produce graft copolymers by other operatingprocedures. In the emulsion polymerization technique for the productionof graft copolymers a latex (usually aqueous) of the polymeric backboneis first prepared by the emulsion polymerization of a suitable monomeror mixture of monomers. To the resulting latex is then added the monomeror mixture of monomers to be graft copolymerized onto the previouslyformed polymeric backbone and the resulting mixture is allowed tointeract under polymerizing conditions to form the graft copolymer.

While the fine details of the mechanism of graft copolymerization havenot all been fully elucidated as yet, in the broad aspects thereof aportion of the monomer (or mixture of monomers) added to the preformedbackbone polymer unite with this polymer at various reactive points onthe extended molecule thereof to form side chains which continue to growas the polymerization reaction proceeds. Other portions of the addedmonomer polymerize to form homopolymers and a portion of thesehomopolymer molecules may react with the preformed polymer as previouslydescribed. If a mixture of monomers is added to the preformed polymer, aportion of the mixture copolymerizes and a portion of the resultingcopolymer molecules may react with the polymeric backbone as previouslydescribed. In addition, a greater or lesser portion (under someconditions, a very considerable portion) of homopolymer molecules formedfrom a single monomer or copolymer molecules formed from a mixture oftwo or more monomers, does not react with the polymeric backbone but,instead, such homopolymer or copolymer molecules continue to grow in thereaction mixture until they reach their termination point and arefinally recovered from the reaction mixture as such homopolymers and/orcopolymers in intimate admixture with the graft copolymer also formed.Similarly, any polymeric backbone molecules that may have escapedreaction with the added monomer or monomers (including homopolymersand/or copolymers formed therefrom) is eventually recovered from thereaction mixture as such,

again in intimate admixture with the other polymeric products formed.

From the above discussion it is evident that for graft copolymerizationto occur it is essential that the polymeric backbone possess reactivepoints on the extended molecule thereof. Polymer molecules of this typeare frequently characterized as unsaturated, this term here having asomewhat broader connotation than usual, embracing not only polymerspossessing chemically unsaturated groupings but also polymers havingactive or labile hydrogen atoms (for example) on the extended moleculesthereof. It the polymeric backbone molecules do not possess suchreactive points (i.e. the polymeric molecules are saturated), graftcopolymerization reactions are not possible. It is evident that if amonomer (or mixture of monomers) is added to a preformed polymer thatdoes not possess reactive points on the extended molecule thereof andthe resulting mixture is allowed to react under polymerizing conditionsthere is finally recovered from the reaction mixture no more than theoriginal preformed polymer and the homopolymers and/ or copolymersproduced by the polymerization of the added monomer or monomer mixture,all in intimate admixture.

However, the essential requirement that the polymeric backbone mustpossess reactive points on the extended molecule thereof for graftcopolymerization to occur results in the production of polymericproducts that do not exhibit environmental stability to the degree thatis'desirable. The resulting graft copolymers still possess some reactivepoints on the extended molecule thereof which result in a more or lessrapid deterioration of the polymeric product on aging, the deteriorationbeing especially rapid when the polymeric product is exposed tosunlight.

I have discovered that use in graft copolymerization of a preformedpolymeric backbone prepared by the copolymerization of a mixture of (a)a major portion of a monomer which, when polymerized alone, produces asaturated polymer and (b) a minor portion of a monomer which, whenpolymerized alone, produces an unsaturated polymer, produces a graftcopolymer exhibiting superior aging characteristics in comparison withgraft copolymers of the prior art. As a corollary of this discovery, Ihave found further that similarly suitable polymeric backbones areproduced by the graft copolymerization of a monomer which, whenpolymerized alone, produces a saturated polymer, onto a comparativelyminor amount of an unsaturated polymer. The resulting graft copolymer,when employed as the polymeric backbone in a subsequent conventionalgraft copolymerization reaction, produces a final graft copolymerexhibiting superior aging characteristics in comparison with graftcopolymers of the prior art.

An object of this invention is to provide polymeric products exhibitinga high degree of environmental stability.

Another object of this invention is to provide polymeric productsexhibiting a high degree of environmental stability produced by thegraft copolymerization techmque.

A further object of this invention is to provide an improved process forthe production of polymeric products by the graft copolymerizationtechnique.

Additional objects of this invention will become apparent as thedescription thereof proceeds.

For the better understanding of this invention a number of illustrativebut non-limiting examples relating thereto are presented. Most of theseexamples comprise illustrative and non-limiting specific embodiments ofthis invention but in some instances results obtained by following priorart teachings are presented and compared with the improved results thatare obtained by following the teachings of the present invention.

V 3 Examples 1-3 Three separate butyl acrylate-butadiene copolymers wereprepared using the following recipes (expressed in parts by weight):

'In the above table, Tergitol penetrant No. 4 is sodium tetradecylsulfate.

For each example, the appropriate recipe as set forth above was chargedinto a pressure tight reactor which was then rotated in a water bathheated to 95 C. for about four hours at which time conversion to theaqueous copolymer latex was essentially complete.

- By the above procedure three separate aqueous latices of polymericbackbones, differing slightly in composition, were obtained. Each ofthese latices was individually subjected to a graft copolymerizationreaction but since the operating techniques and additional reactants(both with respect to identity and amount) were the same in all threeinstances, the following single recipe and description will serve tocover each one of the three separate operations. 7

The following materials (expressed in parts by weight were placed in areactor provided with a reflux condenser, stirrer and an entrance portfor the subsequent introduction of additional materials:

Butyl acrylate-butadiene copolymer (dry basis).-

From Example 1 or 2 or 3 60.0 Dresinate 731 (100% basis) 5.6 Sodiumpyr-rophosphate 0.6 Sodium hydroxide 0.3 Daxad 11 0.25 Dextrose 2.0Distilled water 400.0

Total, including water present in the butyl acrylate-buta dienecopolymer aqueous latex.

In the above table Dresinate 731 is the sodium salt of hydrogenated,disproportionated rosin. Daxad 11 is polymerized sodium salts of alkylnaphthalene sulfonic acids.

The contents of the reactor were stirred and heated to 65 C. by means ofa water bath surrounding the reactor and when this temperature wasreached a solution of 0.025 part by weight ferrous sulfate heptahydrateand 0.2 part by weight ethylenediamine tetraacetic acid sodium saltdissolved in five parts by weight of water was added to the reactor.Following this addition, there was added to the reactor over a period ofone hour a mixture (expressed in parts by weight) comprising:

Styrene 90 Acrylonitrile 50 Cumene hydroperoxide 1.5

During this addition of the mixture of polymerizable monomers andcatalyst the temperature within the reactor was maintained at 65 C. andafter addition of this mixture was complete the reactor contents weremaintained at this temperature level for one more hour. At the end ofthis time reaction was complete as evidenced by the fact that steamdistillation of a sample of the final latex carried no monomer overhead.

After reaction was complete, 2.5 parts by weight 2,2- methylene bis(4-methyl 6-tertiary butyl phenol) (anti oxidant) were added t thereaction mixture which was then cooled to room temperature. The aqueouslatex was coagulated by pouring into 1200 parts by weight watercontaining two parts by weight sodium chloride, two parts by Weight alumand four parts by weight sulfunc acid. The resulting coagulated mixturewas heated to 95 C. to facilitate subsequent filtering and washingoperations and the coagulum was separated by filtration, water washed,and finally dried at 65 C.

The three graft copolymers so produced were individually milled on a tworoll rubber mill (roll temperature, 320 R). All three exhibited goodmilling properties and molded sheets of the individual products wereprepared for determination of physical properties. Certain physical testdata obtained on the resulting translucent It is seen that the impactvalue of the graft copolymers decreased from a high value to a moderatevalue as the proportion of butadiene in the butyl acrylate-butadienecopolymer increased. Even the only moderate impact value obtained whenbutadiene:butyl acrylate were employed in 1:9 radio is considered to beadequate for most applications requiring good resistance to breakage.The heat distortion temperature (softening point) is at a satisfactoryhigh level for all three polymers; the temperature apparently decreasesslightly as the amount of polybutadiene present in the butylacrylate-butadiene copolymer increases. The surface hardness of thepolymers is at a satisfactory high level. There is an apparent largeincrease in the surface hardness as the butadiene:butyl acrylate ratiois increased from 1: 19 to 1:9.

One of the most interesting and important properties exhibited by thegraft copolymers of these examples is that they do not develop surfacecrazing on exterior exposure to sunlight. It is easily possible toproduce graft copolymers using a straight unsaturated polymer backbonethat exhibit impact values, heat distortion temperatures (softeningpoints) and surface hardnesses at least as high as those of the graftcopolymers of the present examples but on exterior exposure to sunlightthese polymers rapidly develop surface crazing.

It will be noted that the composition of the final graft copolymericproducts of the above examples, expressed as percent by weight of thepolymer backbone (dry basis) and monomers employed in the graftcopolymerization operation, is 30% of the butyl acrylate-butadienecopolymer backbone, 45% styrene and 25% acrylonitrile. As would beexpected, useful products are produced over a range in the proportionsof these three ingredients. Thus, useful products are produced whenusing butyl acrylatebutadiene copolymers within the range (expressed aspreviously specified) 20 to 60%, corresponding to a range of to 40% forthe total of the styrene plus acrylonitrile mixture. The styreneingredient may comprise from 30 to 70% of the final graft polymer whilethe acrylonitrile ingredient preferably comprises from 20 to 30% of thefinal graft polymer but may be as low as 10% if desired.

Graft copolymers essentially similar to those of the present examplesmay be prepared by replacing a portion of all the butadiene employed inmaking the butyl acrylate-butadiene copolymer by an equivalent amount ofother conjugated dienes. Among such other dienes may be mentioned2-chlorobutadiene-l,3 (chloroprene), isoprene, piperylene, 2,3-dirnethylbutadiene-l,3 methyl pentadienes, and the like.

Likewise, graft copolymers essentially similar to those of the presentexamples may be prepared by replacing a portion of all the styreneemployed by an equivalent amount of other aromatic compounds such asalpha a eless iiiethyl styrene, vinyl toluene, alpha methyl p-methylstyrene, and the like.

Finally, graft copolymers essentially similar to those of the presentexamples may be prepared by replacing a portion or all of theacrylonitrile employed in the graft copolymerization reaction by anequivlaent amount of methacrylonitrile.

Example 4 This example is presented for the purpose of demonstratingthat in order to obtain graft copolymers exhibiting the propertiesoutlined in the previous examples it is essential that a minor amount ofa conjugated diene be employed to modify the butyl acrylate.

The operating procedure followed in the present example is essentiallythe same as that described in detail in connection with Examples 1-3hereof. Accordingly, the exposition of the present example will belargely confined to reciting differences in reactants, properties of theproduct, etc., between the present example and Examples 1-3.

The following recipe (expressed in parts by weight) Lvas employed toprepare the poly-butyl acrylate backone:

Butyl acrylate 100 Tergitol penetrant No. 4 2.65 Potassium persulfate0.0166 Distilled water 200 Since this reaction mixture did not containany butadiene (gaseous at room temperature) polymerization was hereconducted at the refluxing temperature of the mixture (9097 C.). After1.25 hours at this temperature the reaction was essentially complete asdetermined by coagulating a weighed sample of the resulting reactionmixture and separating, washing, drying and weighing the coagulum.

For the subsequent polymerization reaction a sufiicient portion of theaqueous latex, produced as above set forth, to contain 60 parts byweight (dry basis) poly-butyl acrylate was taken and further processedexactly as described in connection with the polybutadiene modifiedpoly-butyl acrylate latices of Examples 13 and the resulting polymer wasisolated from the final reaction mixture exactly as previouslydescribed.

When an attempt was made to mill the dry polymeric product of thepresent example on a two roll rubber mill (roll temperature 320 F.) itexhibited very poor milling properties. The resulting sheet exhibitedmarked shrinkage after removal from the mill and gave other evidence ofbeing a mere mechanical mixture of incompatible materials. However,molded samples of the material were prepared and subjected to physicaltesting by the same methods set forth in Examples l-3 hereof.

The data obtained in these tests are set forth below:

Notched Izod impact value, ft. lbs/inch notch 10.2 Heat distortiontemperature, C 93.0 Rockwell hardness, R scale 49.0

While this material has a very high impact value and a high heatdistortion temperature (softening point), the low surface hardnessthereof coupled with its very poor milling properties excludes thematerial from consideration as a useful commercial product. The poormilling properties, low surface hardness and lack of clarity of theproduct of this example, all indicate that this material is at leastessentially a mere mechanical mixture of polybutyl acrylate andstyrene-acrylonitrile copolymer.

Example 5 This example is quite similar to Examples 1-3 hereof, themajor change involving the use of ethyl acrylate instead of butylacrylate.

The following recipe, expressed in parts by weight, was

. a employed to prepare the ethyl acrylate-butadiene co polymer:

Ethyl acrylate 99.0 Butadiene 1 .0 Tergitol penetrant No. 4 2.65Potassium persulfate 0.5 Distilled water 200.0

The copolymerization was conducted in the pressure tight reactordescribed in Examples 1-3 and was essentially complete after four hoursat 70 C.

The operating techniques and reaction conditions employed in the graftpolymerization reaction were identical to those employed in Examples 1-3but there was some diiferences in reactants as set forth below.

The primary graft copolymerization mixture (in parts by weight)consisted of:

Ethyl acrylate-butadiene copolymer prepared as above (dry basis) 60.0Dresinate 731 (100% basis) 5.6 Sodium pyrophosphate 0.6 Sodium hydroxide0.3 Dextrose 2.0 Distilled water 400.0

1 Total, including water present in the ethyl acrylatebutw dienecopolymer aqueous latex.

After heating this mixture to 65 C. as previously described, a solutionof 0.025 part by Weight ferrous sulfate heptahydrate and 0.2 part byweight ethylenediamine tetraacetic sodium salt dissolved in five partsby weight water was added.

The monomer-catalyst mixture used here consisted of (in parts byweight):

Styrene Acrylonitrile 5O lCumene hydroperoxide 2.1

This mixture was added as described in Examples 1-3 and the furtherprocessing thereof and the isolation of the polymeric product followedthe procedures of these earlier examples.

The dry graft copolymer exhibited good milling properties and 0.08 inchsheets thereof were fairly clear. The product exhibited a moderatelyhigh impact value and a high and satisfactory surface hardness and heatdistortion temperature (softening point) as the following data show:

Notched Izod impact value, ft. lbs/inch notch 1.4 Rockwell hardness, Rscale 78 Heat distortion temperature, C 90.5

Examples 6 and 7 These examples illustrate the modification ofpolymerized acrylic acid esters by the graft copolymerization of acrylicacid esters onto a preformed polymer of a conjugated diene.

Two separate polymeric backbones were prepared by the graftcopolymerization of butyl acrylate onto a preformed aqueouspolybutadiene latex, using the following recipes, expressed in parts byweight:

Example 6 7 1 Total, including water present the aqueous polybutadienelatex.

In the above table the polybutadiene used was a aqueous polybutadienelatex of about 55% solids content and a pH of 9.5'11.0.

The'above recipes were separately polymerized in a reactor provided withan agitator and reflux condenser, these reaction mixtures being heatedto 95-97 C. by a water bath surrounding the reactor and were polymerizedat this temperature under agitation until reaction was complete. InExample 6, due to the retarding eifect of the rather large quantity ofaqueous polybutadiene latex present, the reaction was rather far fromcompletion after four hours so an additional charge of cumenehydroperoxide (0.0166 part by weight) was added and the reaction wascontinued for 3.5 hours more at which time the reaction was essentiallycomplete. In Example 7, on the other hand, the polymerization reactionwas essentially complete after only 3.5 hours at reaction temperature.

The graft copolymerization reactions were carried out exactly asdescribed in connection with Examples 1-3, both with respect tooperating techniques and nature and quantities of reactants, with theimportant but obvious exception that in Example 6 suflicient of theaqueous graft copolymer latex, prepared as above described under Example6 to furnish 60 parts by weight (dry basis) of the polymer, and inExample 7 suflicient of the aqueous graft polymer latex, prepared asabove described under Example 7, to furnish 60 parts by weight (drybasis) of the polymer, were respectively employed in place of thepolybutadiene modified poly-butyl acrylate latices of Examples l-3.

The isolation and further processing of the final polymeric productsalso followed the procedures described in Examples 1-3. Various physicalproperties and miscellaneous observations on the graft copolymersproduced are tabulated below:

Example 6 7 Fair. --I Very Poor.

Both of these graft copolymers are materials of high impact value, highheat distortion temperature (softening point) and high surface hardness.While these materials can be milled, their milling properties leave muchto be desired and they are deficient with respect to clarity. Neither ofthese graft copolymers deteriorate on exterior exposure to sunlight.

A portion or all of the aqueous polybutadiene latex employed in thepresent examples may be replaced by an aqueous latex containing anequivalent amount of other conjugated diene polymers. Thus, aqueouslatices of polychloroprene, polyisoprene, polypiperylene, poly-dimethylbutadiene and polymerized methyl pentadienes, and the like, may replacepart or all of the polybutadiene latex. V The approximate limits of theranges of the three ingredients employed in the preparation of the finalgraft polymer within which useful products may be obtained havepreviously been set forth in connection with Examples 13 hereof.Likewise, various equivalents of the styrene and acrylonitrile employedin the preparation of 8 the final graft polymer are listed in connectionwith-Examples 13 hereof.

.Useful products are obtained in accordance with the present inventionwhen the ratio of ethyl or butyl acrylate to conjugated diene inthepreparation of the copolymers of Examples 1-3 inclusive and 5 is to 99%by weight of the acrylate and correspondingly 10% to 1% by weight of theconjugated diene. With respect to the graft copolymer backbone ofExamples 6 and 7, useful products are obtained when the ratio of ethylor butyl acrylate to conjugated diene polymer is 75% to by weight of theacrylate and correspondingly 25% to 5% by weight of the conjugated dienepolymer.

Be it remembered, that while this invention has been described inconnection with specific details of specific embodiments thereof, theseare illustrative only and are not to be considered limitations on thespirit or scope of the said invention except insofar as these may beincorporated in the appended claims.

I claim:

1. A graft copolymer product of A. a material selected from the groupconsisting of (1) a copolymer of from 90% to 99% by weight of a materialselected from the group consisting of ethyl acrylate and butyl acrylateand, correspondingly, 10% to 1% by weight of a conjugated diene, and (2)a graft copolymer of from about 75% to about'95% by weight of a materialselected from the group consisting of ethyl acrylate and butyl acrylateand, correspondingly, 25% to 5% by weight of a conjugated diene polymer,and

B. a material selected from the group consisting of styrene, vinyltoluene, alpha methyl styrene and alpha methyl p-methyl styrene, and

C. a material selected from the group consisting of acrylonitrile andmethacrylonitrile,

said graft copolymer product embracing, on the 100 parts dry weightgraft copolymer basis, from about 20 parts to about 60 parts by weight(dry basis) of the combined material selected from group (A), from about30 parts to about 70 parts by weight of the combined material selectedfrom group (B) and from about 10 parts to about 30 parts by weight ofthe combined material selected from group (C).

2. A graft copolymer of A. a copolymer of from 90% to 99% by weight ofethyl acrylate and, correspondingly, 10% to 1% by weight of a conjugateddiene, and

B. a material selected from the group consisting of styrene, vinyltoluene, alpha methyl styrene and alpha methyl p-methyl styrene, and

C. a material selected from the group consisting of acrylonitrile andmethacrylonitrile,

the said graft copolymer embracing, on the 100 parts dry weight graftcopolymer basis, from about 20 parts to about 60 parts by weight (drybasis) of the combined material of group (A), from about 30 parts toabout 70 parts by weight of the combined material selected from group(B) and from about 10 parts to about 30 parts by weight of the combinedmaterial selected from group (C).

3. A graft copolymer of (A) a copolymer of from 90% to 99% by weight ofbutyl acrylate and, correspondingly, 10% to 1% by weight of a conjugateddiene, and (B) styrene and (C) acrylonitrile, said graft copolymerembracing, on the 100 parts dry weight graft copolymer basis, from about20 parts to about 60 parts by weight (dry basis) of the combinedmaterial of group (A), from about 30 parts to about 70 parts by weightof combined styrene and from about 10 parts to about 30 parts by weightof combined acrylonitrile.

4. A graft copolymer of (A) a copolymer of from 90% to 99% by weight ofethyl acrylate and, c0rrespond ingly, 10% to 1% by weight of butadiene,and (B) styrene and (C) acrylonitrile, said graft copolymer em- 9bracing, on the 100 parts dry weight graft copolymer basis, from about20 parts to about 60 parts by weight (dry basis) of the combinedmaterial of group (A), from about 30 parts to about 70 parts by weightof combined styrene and from about 10 parts to about 30 parts by weightcombined acrylonitrile.

5. A graft copolymer product of (A) an intermediate graft copolymer offrom about 75% to 95 by weight of ethyl acrylate and, correspondingly,25% to by weight of polybutadiene, (B) styrene and \(C) acrylonitrile,said graft copolymer product embracing, on the 100 parts dry weightgraft copolymer basis, from about 20 parts to about 60 parts by weight(dry basis) of the combined material selected from group (A), from about30 parts to about 70 parts by weight of combined styrene and from aboutparts to about 30 parts by weight combined acrylonitrile.

6. A graft copolymer of A. a copolymer of from 90% to 99% by weight ofbutyl acrylate and, correspondingly, 10% to 1% by weight of a conjugateddiene, and

B. a material selected from the group consisting of styrene, vinyltoluene, alpha methyl styrene and alpha methyl pmethyl styrene, and

C. a material selected from the group consisting of acrylonitrile andmethacrylonitrile,

the said graft copolymer embracing, on the 100 parts dry weight graftcopolymer basis, from about 20 parts to 10 about parts by weight (drybasis) of the combined material of group (A), from about 30 parts toabout parts by weight of the corn-bined material selected from group (B)and from about 10 parts to about 30 parts by weight of the combinedmaterial selected from group (C).

7. A graft copolymer product of (A) an intermediate graft copolymer offrom about to by weight of butyl acrylate and, correspondingly, 25% to5% by weight of polybutadiene, (B) styrene and (C) acrylonitrile, saidgraft copolymer product embracing, on the parts dry weight graftcopolymer basis, from about 20 parts to about 60 parts by weight (drybasis) of the combined material selected from group (A), from about 30parts to about 70 parts by weight of combined styrene and from about 10parts to about 30 parts by weight combined acrylonitrile.

References Cited in the file of this patent UNITED STATES PATENTS2,232,515 Arnold et al. Feb. 18, 1941 2,356,091 Roedel Aug. 15, 19442,802,808 Hayes Aug. 13, 1957 FOREIGN PATENTS 456,442 Great Britain Aug.8, 1935 767,642 Great Britain Feb. 7, 1957 778,265 Great Britain July 3,1957

1. A GRAFT COPOLYMER PRODUCT OF A. A MATERIAL SELECTED FROM THE GROUPCONSISTING OF (1) A COPOLYMER OF FROM 90% TO 99% BY WEIGHT OF A MATERIALSELECTED FROM THE GROUP CONSISTING OF ETHYL ACRYLATE AND BUTYL ACRYLATEAND, CORRESPONDINGLY, 10% TO 1% BY WEIGHT OF A CONJUGATED DIENE, AND (2)A GRAFT COPOLYMER OF FROM ABOUT 75% TO ABOUT 95% BY WEIGHT OF A MATERIALSELECTED FROM THE GROUP CONSISTING OF ETHYL ACRYLATE AND BUTYL ACRYLATEAND, CORRESPONDINGLY, 25% TO 5% BY WEIGHT OF A CONJUGATED DIENE POLYMER,AND B. A MATERIAL SELECTED FROM THE GROUP CONSISTING OF STYRENE, VINYLTOLUENE, ALPHA METHYL STYRENE AND ALPHA METHYL P-METHYL STYRENE, AND C.A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ACRYLONITRILE ANDMETHACRYLONITRILE, SAID GRAFT COPOLYMER PRODUCT EMBRACING, ON THE 100PARTS DRY WEIGHT GRAFT COPOLYMER BASIS, FROM ABOUT 20 PARTS TO ABOUT 60PARTS BY WEIGHT (DRY BASIS) OF THE COMBINED MATERIAL SELECTED FROM GROUP(A), FROM ABOUT 30 PARTS TO ABOUT 70 PARTS BY WEIGHT OF THE COMBINEDMATERIAL SELECTED FROM GROUP (B) AND FROM ABOUT 10 PARTS TO ABOUT 30PARTS BY WEIGHT OF THE COMBINED MATERIAL SELECTED FROM GROUP (C).